25. • Formed from sediments
(rock fragments, mineral
grains, animal & plant
remains) that are pressed
or cemented together or
when sediments precipitate
out of a solution.
26. • These sediments are moved by wind,
water, ice or gravity.
• Sedimentary rocks represent 7% of the
Earth’s crust, but they cover 70% of the
• Sedimentary rocks are fossil-carrying
27. What turns sediments into solid rock?
• Water or wind breaks down and
deposits sediment (erosion &
28. • The heavy sediments press down on
the layers beneath (compaction)
30. How can sedimentary layers help us
understand the age of fossils?
• As sedimentary rocks
are deposited, they
• Scientists know that
the layers on top
(and the fossils in
the top layer) are
YOUNGER than the
fossils in lower
31. 3 Types of Sedimentary
• Clastic (also called Detrial)—made of
broken pieces of other rocks
32. Organic—remains of plants and animals
are deposited in thick layers
• Fossil rich limestone is made from the
shells of ocean animals; used to make
3 Types of Sedimentary
33. • Chemical—minerals dissolved in
lakes, seas, or underground
3 Types of Sedimentary
Mineral crystals are made as the shallow water that has
flooded the bottom of Death Valley evaporates.
Click on image for full size (66K JPG)
Courtesy of Martin Miller, University of Oregon
35. • Rocks that have changed due to
intense temperature and pressure
• “Meta” means “change” and morphosis
means “form” in Greek
• Igneous, sedimentary and other
metamorphic rocks can change to
become metamorphic rocks
36. What occurs in the Earth to
change these rocks?
• Pressure from overlying rock layers
• High heat, but not enough to melt the rock
• Rocks may be flattened or bent or atoms may
be exchanged to form new minerals.
37. How are metamorphic rocks classified?
• Foliated—mineral grains are flattened
and line up in parallel bands
• Example: gneiss formed from
rearrangement of minerals in granite
38. How are metamorphic rocks classified?
• Non-Foliated—No bands are formed
• Example: marble formed from limestone
39. Where do metamorphic rocks
• Where magma intrudes relatively
• Near colliding plates (near
• Places that are covered miles
thick with other rock causing
• When hot water intrudes rock
• Where a meteorite strikes
• Where lightning bolts strike